The present invention relates to improvements in transmissions which can be employed with advantage in the power trains of motor vehicles to transmit torque from a prime mover (such as an internal combustion engine) to the wheels. More particularly, the invention relates to improvements in transmissions which comprise clutches, actuators, torque sensors, pulleys, belts or chains and/or other parts controlled by systems of pumps, valves and other fluid flow initiating and regulating devices.
It is often necessary to convey a fluid (e.g., oil or another hydraulic fluid) between parts which must move with and/or relative to each other, e.g., between a stationary component and a rotary component or between two components which can or must or should rotate at different speeds an/or in different directions. Transmissions wherein a conduit, a pipe, a hose or an analogous fluid conveying component must confine a stream of a fluid to flow between two spaced-apart components which can or should move relative to each other are well known in the art of power trains for motor vehicles.
It is also known to mount the fluid conveying component (hereinafter called conduit for short) in such a way that it can further serve as a means for compensating for manufacturing tolerances and/or for improper centering of one of the two spaced-apart components relative to the other component (and/or vice versa) and/or for pronounced or unanticipated or normal wear upon the spaced-apart components. In accordance with a presently known proposal, one end portion of a small-diameter conduit is introduced into a bore of one of two spaced-apart components, and the other end portion of such conduit is confined in a bore of the other of the two spaced-apart components. Each end portion is surrounded by a split-ring piston packing which is intended to seal the end portion of the respective bore. Each such packing is further intended to act as a constituent of a universal joint which enables the respective component to perform at least some stray movements (i.e., movements other than strictly angular movements) relative to the other component. Such stray movements might be necessary to account or to compensate for certain manufacturing tolerances and/or for wear and/or for lack of accurate centering of the end portions of the conduit in the bores of the respective components. As a rule, the ability of the end portions of the conduit and of the split-ring piston packings to act as parts of a universal joint is enhanced by enlarging those portions of the bores which receive the packings.
A drawback of such connections for the end portions of the conduit is that the universal joints permit pronounced and often excessive leakage of the conveyed fluid. This can entail a penetration of a coolant or a lubricant or a force transmitting fluid agent into certain parts of a power train which should not be lubricated and/or cooled and/or wetted. Furthermore, the escaping fluid must be replaced at frequent intervals, or the reservoirs for such fluid must be designed to confine large quantities of oil or another fluid medium.
An object of the invention is to provide a novel and improved combination of parts which can be utilized to convey a fluid, particularly oil or another hydraulic fluid, to or from one or more consumers and which must or should be free to move relative to each other.
Another object of the invention is to provide a novel and improved method of reducing or eliminating leakage of a fluid which can or which must be conveyed at an elevated pressure along a path defined by parts that are movable relative to each other.
A further object of the invention is to provide a novel and improved method of reducing or eliminating leakage of a pressurized fluid from a path which is defined by parts that should be capable of performing axial and/or angular and/or other types of movements (such as universal movements) relative to each other.
An additional object of the invention is to provide a novel and improved system of valves, pressure gauges, flow restrictors and/or other means for regulating the flow of a pressurized fluid from one or more pumps and/or other sources to one or more consumers, such as fluid-operated clutches, fluid-operated actuators (e.g., cylinder and piston units) and/or others.
Still another object of the invention is to provide a novel and improved system for cooling one or more fluid-operated clutches, cylinder-and-piston units and/or other fluid-consuming or fluid-operated constituents of motor vehicles, particularly of power trains for use in motor vehicles.
A further object of the invention is to provide a novel and improved transmission, such as a continuously variable transmission (known as CVT), particularly for use in the power trains of motor vehicles.
Another object of the invention is to provide a novel and improved system for regulating the flow of a hydraulic fluid between a pump, one or more consumers, and a sump in the power train of a motor vehicle.
An additional object of the invention is to provide a fluid flow regulating system which ensures a highly accurate, predictable and at least substantially leakage-free flow of a pressurized fluid from one or more pumps, accumulators and/or other sources to one or more consumers and from the consumer(s) back to the source(s) of pressurized fluid or to reservoirs for confinement of the fluid which is to be pumped to one or more consumers.
Still another object of the invention is to provide a transmission which is constructed and assembled in such a way that the flow of a pressurized or spent hydraulic fluid can be regulated with a maximum degree of accuracy under circumstances which are most likely to develop, again and again, in actual use of the transmission.
A further object of the invention is to provide a novel and improved transmission which employs a plurality of starting clutches, such as at least two disc clutches.
Another object of the invention is to provide a novel and improved method of repeatedly circulating a body of oil or another hydraulic fluid through one or more pumps, reservoirs, sumps, conduits and consumers in a transmission, such as a continuously variable transmission with adjustable pulleys and an endless chain or belt trained over such pulleys.
An additional object of the invention is to provide a novel and improved combination of valves, flow restrictors, fluid flow and fluid pressure monitoring gauges and like constituents for use in conjection with the starting clutch or clutches and/or fluid-operated actuator means of transmissions for use in the power trains of motor vehicles.
Still another object of the invention is to provide a motor vehicle, such as a passenger car or a van or a truck, wherein the power train embodies a transmission of the above outlined character.
A further object of the invention is to provide novel and improved valves and combinations of two or more valves for use in transmissions of the type wherein one or more friction clutches (such as disc clutches), one or more cylinder-and-piston units and/or other fluid-operated parts must receive and must be relieved of predetermined quantities of pressurized hydraulic fluids.
One of several features of the instant invention resides in the provision of a fluid conveying structure which can be utilized in the transmission of the power train in a motor vehicle and comprises a first component having a first socket (such as the end portion of a through bore), a second component having a second socket (e.g., the end portion of a through bore), a conduit having a first end portion in the first socket and a second end portion in the second socket, at least one first sealing element which is interposed between the first component and the first end portion in the first socket with freedom of rotation of the first component and the first end portion of the conduit relative to each other, and at least one second sealing element which is interposed between the second component and the second end portion in the second socket and is arranged to prevent rotation of the second component and the second end portion of the conduit relative to each other.
The first component, the second component and/or the conduit can form part of a transmission.
It is preferred to select the material of the at least one second sealing element in such a way that this sealing element is resiliently deformable and is located between the second component and the second end portion of the conduit in a deformed condition so that it bears upon the second component and the second end portion of the conduit with a force which is sufficient to compel the second component and the second end portion of the conduit to share rotary movements.
The first end portion of the conduit has an external surface which is located in the first socket and can be provided with a circumferential groove for a piston packing (such as a split-ring piston packing) forming part of or constituting the at least one first sealing element.
An external surface of the second end portion of the conduit is located in the second socket and can be provided with a circumferential groove for the at least one second sealing element (e.g., an O-ring).
The wall thickness of one end portion of the conduit (as measured radially of the conduit) is or can be different from the wall thickness of the other end portion of the conduit. It is often preferred to select the dimensions of the conduit in such a way that the wall thickness of its first end portion exceeds the wall thickness of the second end portion.
An internal stop of the second component can constitute an abutment for the end face at the second end portion of the conduit to thus limit the extent of lengthwise movement which the conduit can perform in a direction from the first component toward the second component, e.g., when the conduit is being acted upon by a fluid flowing into the first end portion and toward the second end portion of the conduit.
The central longitudinal axis of the conduit can coincide with the axes of the two sockets, and the internal stop can constitute an annular internal shoulder of the second component in the deepmost portion of the second socket. The first and second components and the conduit can be mounted for rotation about a common axis, and the improved structure can further comprise means (e.g., the output element of an engine or the output element of a friction clutch in the power train of a motor vehicle) for rotating the first component at a first speed n1, and means for rotating the second component at a speed n2 which is less than the first speed n1. The arrangement can be such that the speed n1 can exceed the speed n2 and the latter can equal n3 (which is the speed of the conduit). Alternatively, the speed n2 can match the speed n3 and can exceed the speed n1. It is also possible to select the speeds in such a way that n1 exceeds zero speed but the speeds n2 and n3 are zero. At least one of the components can rotate about the central longitudinal axis of the conduit.
Another feature of the invention resides in the provision of a transmission which can be utilized in the power train of a motor vehicle and comprises a clutch (such as a starting clutch) having a cylinder defining a chamber, a piston which is movable in the chamber, a clutch disc having a portion disposed in the chamber and including a first side adjacent the piston and a second side, and first energy storing means acting upon the second side of the clutch disc (against a variable pressure of a fluid in the chamber) in a direction to expel fluid from the chamber. The transmission further comprises means for supplying to the chamber a fluid at the aforementioned variable pressure, and such fluid supplying means comprises a source (e.g., a pump) of pressurized fluid, means for connecting the source with the chamber, a pressure reducing valve having a housing which is associated with the connecting means (the housing can be installed in the connecting means), a valving element which is movable in the housing between a plurality of positions, and second energy storing means serving to yieldably urge or bias the valving element to a predetermined position in which the pressure of fluid in the cylinder chamber counteracts the bias of the first energy storing means, and a control valve which operates to determine the positions of the valving element. The control valve can assume a plurality of different conditions including a preselected condition in which the control valve exerts no appreciable influence (if any) upon the valving element to thus permit the valving element to assume its predetermined position under the influence of the second energy storing means.
The connecting means of the just described transmission can comprise a first component having a first socket, a second component having a second socket, a conduit having a first end portion in the first socket and a second end portion in the second socket, at least one first sealing element which is interposed between the first component and the first end portion of the conduit in the first socket with freedom of rotation of the first component and the first end portion of the conduit relative to each other, and at least one second sealing element which is interposed between the second component and the second end portion of the conduit in the second socket and is arranged to prevent rotation of the second component and the second end portion of the conduit relative to each. The two components and the conduit jointly define an elongated path for the flow of fluid between the source and the chamber of the cylinder in the clutch.
The housing of the pressure reducing valve can be provided with a first inlet (e.g., a port) which is arranged to receive fluid from the control valve (or which can receive fluid at a rate and/or at a pressure determined by the control valve), a second inlet (e.g., a port) which is arranged to receive fluid from the source (e.g., from a pump at system pressure), an outlet which is communicatively connectable with the source of pressurized fluid by way of the second inlet, and a third inlet (e.g., a port) communicating with the outlet. The valving element of the pressure reducing valve has a first surface which is being acted upon by the energy storing means as well as by fluid which is supplied by or under the influence of the control valve by way of the first inlet to urge the valving element to a position in which the outlet communicates with the second inlet, and a second surface which is being acted upon by fluid entering the housing by way of the third inlet when the outlet communicates with the second inlet to thus urge the valving elementxe2x80x94against the bias od the second energy storing means and against the pressure of fluid upon the first surfacexe2x80x94to a position in which the second inlet is sealed from the outlet.
The valving element of the pressure reducing valve can be arranged to seal the second inlet from the outlet when the pressure of fluid in the chamber at least approximates the bias of the first energy storing means.
The second energy storing means can comprise at least one coil spring. The first face of the valving element in the housing of the pressure reducing valve can constitute an end face of such valving element, and the housing can be provided with a compartment which is adjacent the end face of the valving element and communicates with the first inlet.
The transmission can further comprise a second pressure reducing valve which is installed in the connecting means between the source and the control valve to reduce the pressure of fluid which is being supplied by the source to the control valve so that the pressure of fluid at the first inlet is maintained within a range of between zero pressure and a predetermined maximum pressure.
The clutch can constitute a disc clutch, particularly a clutch having a first set of clutch discs mounted on a first rotary carrier and a second set of clutch discs mounted on a second carrier which can rotate with or relative to the first carrier.
The first energy storing means can comprise at least one diaphragm spring.
A third feature of the invention resides in the provision of a transmission, particularly for use in a power train of a motor vehicle. The improved transmission comprises at least one fluid-operated engageable and disengageable clutch (such as a starting clutch) including a cylinder and a piston which is movable in the cylinder, at least one source of pressurized fluid, conduit means connecting the source with the cylinder, an adjustable pressure regulating valve in the conduit means, an adjustable safety valve in the conduit means between the pressure regulating valve and the cylinder, and means for adjusting the at least one safety valve (such adjusting means can comprise at least one control valve or pilot valve).
The safety valve can include a slide valve having a housing and a valving element (e.g., in the form of a spool) movable in the housing of the slide valve by the at least one pilot (control) valve. The spool of the slide valve is movable to a position in which the safety valve establishes communication between a chamber of the cylinder and the pressure regulating valve. It is further desirable that the spool be also movable to a second position in which the safety valve prevents the flow of fluid between the chamber of the cylinder and the pressure regulating valve and connects the chamber with a sump to thus reduce the presssure of fluid in the chamber.
In accordance with a desirable feature of the just described transmission, the pilot valve or control valve is arranged to adjust the safety valve as well as the pressure regulating valve. For example, the pilot valva can be arranged to furnish to the pressure regulating valve and to the safety valve fluid at a plurality of different pressures including an elevated pressure to thereby change the condition of the safety valve, a low pressure at which the condition of the pressure regulating valve remains unchanged, and a median pressure to thus change the condition of the pressure regulating valve.
An additional feature of the invention resides in the provision of a transmission, particularly for use in a power train of a motor vehicle, which comprises first and second fluid-operated engageable and disengageable clutches each of which includes a cylinder and a piston movable in the respective cylinder, at least one pump or another suitable source of pressurized fluid, conduit means connecting the at least one source with the cylinders of the two clutches, a pressure regulating valve in the conduit means, an adjustable safety valve in the conduit means between the pressure regulating valve and the cylinders (as seen in the direction of fluid flow from the source toward the cylinders), means for adjusting the safety valve, including at least one pilot valve, and a selecting valve in the conduit means between the safety valve and the cylinders. The selecting valve is arranged to assume a first condition in which the conduit means can supply fluid only to the cylinder of the first clutch and a second condition in which the conduit means can supply fluid only to the cylinder of the second clutch.
Such transmission can further comprise at least one fluid pressure monitoring device (e.g., a signal transmitting pressure gauge) which is installed in the conduit means upstream of the selecting valve, as seen in the direction of fluid flow toward the cylinders.
One of the clutches can constitute a forward drive clutch. Furthermore, at least one of the clutches can constitute a reverse drive clutch.
Still another feature of the invention resides in the provision of a variable-speed transmission which can be utilized with particular advantage in the power train of a motor vehicle and comprises at least one fluid-operated clutch including a cylinder and a piston movable in a chamber of the cylinder, means for cooling the at least one clutch, at least one fluid-operated actuator, at least one source of pressurized fluid, conduit means connecting the at least one source with the at least one clutch and the at least one actuator, an adjustable slide valve which is installed in the conduit means and includes a housing and a valving element movable in the housing between a plurality of positions, and means for adjusting the slide valve including a pilot valve or control valve arranged to move the valving element of the adjustable slide valve (a) to a first position in which the slide valve permits fluid to flow from the cylinder and from the at least one actuator to the at least one source, and (b) a second position in which the slide valve establishes a path for the flow of fluid to a pump (such as a suction type jet pump) which is arranged to supply fluid to the cooling means.
The at least one source can include a second pump.
The conduit means can include a bypass conduit arranged to convey fluid to the jet pump in the second position of the valving element, and such transmission can further comprise at least one flow restrictor (e.g., a standard throttle) in the bypass conduit.
The transmission can further comprise an adjustable safety valve which is provided in the conduit means between the slide valve on the one hand, and the cylinder and the at least one actuator on the other hand.
The safety valve is or can be adjustable by the pilot valve. Such pilot valve can be arranged to furnish to the slide valve and to the safety valve fluid at a plurality of different pressures including, for example, a high pressure (e.g., a maximum pressure) to thereby change the condition of the safety valve, a minimum pressure (e.g., zero pressure) at which the condition of the slide valve remains unchanged, and a medium pressure to thus change the condition of the slide valve.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved transmission itself, however, both as to its construction and the mode of assembling, adjusting and operating the same, together with numerous additional important novel and advantageous features thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.